The present invention relates in general to a variable electronic component, and more particularly, to a variable trimmer capacitor adapted to provide an operative range of impedance characteristics by advancing an internal piston in response to the operation of a sealed drive element using an implement such as a screw driver or the like.
In the advancing technologies of computers, testing equipment, appliances and other fields, various types of hybrid electronic circuits, integrated electronic circuits, micro strip amplifiers, micro electronic systems and other electronic devices are being developed and which are being made on increasingly smaller scale and size than has been known heretofore. In accomplishing this end, these devices are generally mounted on small flat insulating bases known as substrates. These various devices incorporate or have formed therein or co-act with various types of electronic components such as inductors, capacitors, resistors, potentiometers, etc., which in turn must be as small as possible to meet the demands of the reduced scale or size of these devices.
The known miniature devices have reached their functional limit even with the best precision manufacturing techniques because certain elements of these devices cannot be reduced further at reasonable cost for commercially acceptable regularly usable devices. For example, the presently known variable trimmer capacitors used in miniature electronic circuits require a mounting frame and a tuning mechanism. There is a limit as to how these elements can be miniaturized and still provide effective and proper function. Further, the mounting elements and tuning mechanisms, when connected in miniature electronic circuits handling high frequencies create unwanted inductance and capacitance in the systems and devices in which they are used because they form stray current paths when placed in close proximity to each other, as may be required in miniature systems or small electronic designs, thereby producing unwanted circuit interaction such as excessive coupling.
U.S. Pats. Nos. 3,679,940 and 3,757,266, which patents are assigned to the same assignee of the within invention, each disclose variable electronic components, such as capacitors and resistors, which are particularly adapted to meet and overcome the problems of these known devices by eliminating the area and mass of conventional mounting frames, tuning mechanisms and other elements heretofore used, and instead integrate the elements of these variable electronic components directly into the circuit. These components are primarily designed as low-profile structures exceedingly small in size, simple in construction, easily adjustable, reliable, in operation, easily replaceable and reproduceable in quantity without sacrificing uniformity or performance.
However, owing to the exceedingly small size of these variable electronic components, the ability to readily adjust these components have likewise become exceedingly more difficult. These components have been provided with an upturned tab to be engaged by a suitable adjustable tool, for example, a tweezer, so as to effect the desired operative range of impedance characteristics of the component. As these components become increasingly smaller in size, it can be appreciated that there is a need to provide a more accurate and reliable means of providing the requisite adjustment. To this end, there has been included in these variable electronic components a rack and pinion assembly operable upon rotation by a miniature screw driver. However, the extremely small size of these components have rendered the construction of a rack and pinion assembly having extremely small gear teeth relatively difficult and expensive, subject to breakage and stripping, and thereby rendering its use less than desirable.
One such variable electronic component which overcomes the aforementioned disadvantages is known from U.S. Pat. No. 4,575,779, which patent is assigned to the same assignee of the within invention. This known variable electronic components is constructed to include an eccentric whose rotational motion imparts reciprocal movement to an impedance-bearing member. The eccentric is operative by engagement with an implement such as a screw driver and the like. However, the elements of this variable electronic component are not contained within the housing, and are therefore exposed to the environment which can effect the component's impedance characteristics due to corrosion and other such action over time.
A sealed variable electronic components, in the nature of a capacitor, is known from U.S. Pats. No. 3,483,450 and U.S. Pat. No. Re. 30,406, the former patent being assinged to the same assignee of the within invention. The latter known capacitor is provided with an end enclosure cap to provide the sealing function. This, of necessity, mandates that the cap be removed each time an adjustment is required, in addition to preventing the use of a shaft to provide for outside adjustment of the capacitor using a knob and the like. As to the former known variable capacitor, its construction results in a relatively long internal high-frequency current path which limits its practical resonance frequency of operation between 1.2 and 1.5 GHz.
Accordingly, it can be appreciated that there is an unsolved need for a sealed variable electronic component, such as a variable trimmer capacitor, which can provide a desired operative range of impedance characteristics, for example, up to 10 GHz, quickly, simply and inexpensively by adjustment using a suitable implement such as a screw driver and the like.